Gradients need not only be limited to changes in organic solvents but also can in addition or by themselves be pH gradients.
There is therefore a need for a generic strategy for choice of gradient solvents in HSCCC.
The variations possible in biphasic solvent immiscibility is shown below.
Slide 13 shows totally miscible solvents and totally immiscible solvents. Slide 14 shows partially immiscible solvents where no relative density differences between upper and lower layer occurs as gradient solvent modifier is added and an example of a chloroform gradient where an inversion of an upper aqueous layer to a lower aqueous layer occurs as the organic gradient modifier is progressively added.
Examples on Slide 13 have no application in CCC whilst the first example on